Prognostic value of EIF5A2 in solid tumors: A meta-analysis and bioinformatics analysis

Abstract Aims In cancer biology, the aberrant overexpression of eukaryotic translation initiation factor 5A2 (EIF5A2) has been correlative with an ominous prognosis, thereby underscoring its pivotal role in fostering metastatic progression. Consequently, EIF5A2 has garnered significant attention as a compelling prognostic biomarker for various malignancies. Our research endeavors were thus aimed at elucidating the utility and significance of EIF5A2 as a robust indicator of cancer outcome prediction. Method An exhaustive search of the PubMed, EMBASE, and Web of Science databases found relevant studies. The link between EIF5A2 and survival prognosis was examined using hazard ratios and 95% confidence intervals. Subsequently, The Cancer Genome Atlas (TCGA) and the Gene Expression Profiling Interactive Analysis (GEPIA) databases were employed to validate EIF5A2 expression across various cancer types. Results Through pooled analysis, we found that increased EIF5A2 expression was significantly associated with decreased overall survival (OS) and disease-free survival/progression-free survival/relapse-free survival (DFS/PFS/RFS). Moreover, TCGA analysis revealed that EIF5A2 was significantly upregulated in 27 types of cancer, with overexpression being linked to shorter OS in three, worse DFS in two, and worse PFS in six types of cancer. GEPIA showed that patients with EIF5A2 overexpression had reduced OS and DFS. Conclusions In solid tumors, EIF5A2 emerges as a reliable prognostic marker. Our meta-analysis comprehensively analyzed the prognostic value of EIF5A2 in solid tumors and assessed its efficacy as a predictive marker.


Introduction
Eukaryotic translation initiation factor 5A (EIF5A), an essential protein, plays a vital role in maintaining cellular polyamine homeostasis and influencing ribosomal peptidyl-transferase [1].Eukaryotic translation initiation factor 5A2 (EIF5A2), a variant of EIF5A, enhances signal transducer and activator of transcription 3 (STAT3) entry into the nucleus.This, in turn, increases STAT3 enrichment on the promoter of transforming growth factor-β1 (TGF-β1), resulting in upregulated TGF-β1 expression and facilitating the epithelial-mesenchymal transition (EMT) [2].EMT enables tumor cells to transition between epithelial and mesenchymal states, which is critical for cancer metastasis [3].Elevated EIF5A2 levels have been detected in various cancers, where it promotes cancer spread and presents as a promising target for cancer treatment [4].Inhibition of EIF5A2 has been shown to suppress tumor development and metastasis, while also overcoming chemotherapy resistance [5].
As scientific knowledge continues to expand, we gain a better understanding of the complex mechanisms underlying cancer metastasis.However, some aspects of these mechanisms remain elusive, underscoring the urgent need for continued research aimed at elucidating them and identifying novel biomarkers for cancer treatment.EIF5A2 is a promising candidate as a prognostic marker for cancer, but the findings from previous studies have not been consistent, making it difficult to establish its predictive significance definitively.To address this issue, in this study, we conducted a metaanalysis to evaluate the predictive value of EIF5A2 in solid tumors and assess its potential as a reliable predictive marker.

Search strategy
We conducted a systematic search of the PubMed, Web of Science, and EMBASE databases to retrieve relevant publications up until February 10, 2023.The search utilized the keywords "EIF5A2" and "cancer" OR "carcinoma" OR "neoplasm" OR "tumor" OR "tumour," along with "prognosis" OR "prognostic" OR "survival" OR "outcome."No language restrictions were applied to the search.We reviewed titles, abstracts, full-text manuscripts, and references to identify relevant studies.As this study did not involve human participants, informed consent was not required (Table 1).

Study selection
We included publications that investigated the relationship between EIF5A2 and survival prognosis in solid tumors, reported measurements of EIF5A2 expression in tissue or blood, and provided sufficient data to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).Our study encompasses a variety of detection methods, ensuring that a broad spectrum of research is included.While real-time PCR is acknowledged as a common method, other detection techniques were also considered, enhancing the diversity of the literature reviewed.Studies that did not provide enough information to estimate HRs and 95% CIs, as well as reviews, case reports, letters, abstracts, animal studies, public database datasets, and duplicated or overlapped research, were excluded from our analysis.Literature in languages other than English or Chinese was excluded due to limitations in linguistic proficiency.Our study prioritized articles that explicitly reported HRs in their findings.Articles relying solely on Kaplan-Meier curves for survival analysis were intentionally excluded from our study.

Data extraction & quality assessment
We extracted relevant data from each eligible study, including author name, publication year, and country of sample origin.Additionally, we collected information on the type of tumor samples, sample size, detection methods, and other characteristics.We also obtained overall survival (OS), disease-free survival/progression-free survival/relapse-free survival (DFS/PFS/ RFS), HRs, and their corresponding 95% CIs.When available, multivariate analysis was preferred over univariate analysis for increased precision.The quality of each study was assessed using the Newcastle-Ottawa Quality Assessment Scale to evaluate its effectiveness.Web of Science ("EIF5A2") and ("cancer" OR "carcinoma" OR "neoplasm" OR "tumor" OR "tumour") and ("prognosis" OR "prognostic" OR "survival" OR "outcome") 83 PubMed ("EIF5A2") and ("cancer" OR "carcinoma" OR "neoplasm" OR "tumor" OR "tumour") and ("prognosis" OR "prognostic" OR "survival" OR "outcome") 66 Embase ("EIF5A2") and ("cancer" OR "carcinoma" OR "neoplasm" OR "tumor" OR "tumour") and ("prognosis" OR "prognostic" OR "survival" OR "outcome")

Statistical analysis
We used HRs and their corresponding 95% CIs to calculate the pooled data in our analysis, directly utilizing the values reported in each study.To assess heterogeneity, I 2 or p-value was used.When I 2 was less than 50% or p-value was larger than 0.05, a fixed-effects model was employed, and when I 2 was greater than 50% or p-value was less than 0.05, a random-effects model was employed.Sensitivity analysis was conducted to assess the reliability of the results.To assess publication bias, funnel plots and Egger's test were used.STATA 17.0 software was used for all data analyses (Stata Corporation, TX, USA).P-values lower than 0.05 were deemed statistically significant.

Bioinformatics analysis
We collected RNA-sequencing expression (level 3) profiles and corresponding clinical information from The Cancer Genome Atlas (TCGA) database (https://portal.gdc.cancer.gov/) for 10,030 patients with various types of cancer.Additionally, we obtained mRNA expression data from paired normal tissue samples in these tumors.Normal tissue samples were also retrieved from the GTEx V8 release version (https://gtexportal.org/home/datasets) for comparison.We used univariate Cox regression analysis and the "forestplot" R package in R version 4.0.3 to display p-values, HRs, and their respective 95% CIs for each variable.The Gene Expression Profiling Interactive Analysis (GEPIA) tool (http://gepia.cancer-pku.cn/),based on TCGA and GTEx data, was used to evaluate abnormal EIF5A2 expression in cancer tissues.We then obtained survival plots in the form of Kaplan-Meier curves for the association between EIF5A2 expression and OS or DFS.P-values less than 0.05 were considered statistically significant.

Search results
Our search strategy yielded a total of 224 articles from the designated databases.After removing 19 duplicates, we screened 205 articles for additional information using our selection criteria, resulting in the elimination of 184 articles and leaving 21 articles for further screening.Of these, two articles did not provide sufficient data, and two others used data obtained from public databases.Ultimately, our meta-analysis included 17 articles published between 2009 and 2022.Figure 1 illustrates the search strategy flowchart.

Study characteristics
A total of 3,554 samples were included in our meta-analysis, with sample sizes ranging from 72 to 436 per study.Various malignancies were investigated, including ovarian cancer, BUC, UTUC, melanoma, prostate cancer, OSCC, ESCC, GC, HCC, GBC, ICC, pancreatic adenocarcinoma, CRC, NPC, cervical cancer, and NSCLC.In 20 studies, the overexpression of EIF5A2 was detected in tissue samples using immunohistochemistry. Table 2 provides fundamental information regarding the included literature.

High EIF5A2 expression & OS
Fourteen studies examined the association between high EIF5A2 expression and prognosis using OS.As there was no significant heterogeneity observed in this analysis (I 2 = 0), a fixed-effects model was used to estimate the pooled HR with a 95% CI.The results showed that high EIF5A2 expression was substantially linked with shorter OS (HR: 1.97; 95% CI: 1.73-2.22),as depicted in Figure 2.

Subgroup analysis for OS
Subgroup analyses were conducted according to tumor type, race, and sample size.The findings of these subgroup analyses are presented in Table 3.In terms of tumor types, high EIF5A2 expression was associated with poor OS in digestive system tumors, with an HR of 1.89 (95% CI:

High EIF5A2 expression & lymph node metastasis
To further explore the association between EIF5A2 and lymph node metastasis, we performed a thorough analysis by compiling data on high EIF5A2 expression and lymph  node (LN) metastasis status.The findings indicated there is no association between elevated EIF5A2 expression and LN status (LN positive vs LN negative), as evidenced by an odds ratio (OR) of 1.14 (95% CI: 0.76-1.52)(Figure 4).

Sensitivity analysis
To assess the robustness of the findings, a sensitivity analysis was conducted by removing each study individually.The results, as depicted in Figures 5 and 6, did not show any significant alteration from the overall analysis, indicating the stability of the results.

Publication bias
To assess publication bias for OS or DFS/PFS/RFS, the study used funnel plots and Egger's test to generate statistical evidence (Figure 7).The results indicated a significant publication bias, with Egger's test p-values of 0.011 for OS (Figure 8a) and 0.006 for DFS/PFS/RFS (Figure 8b).To further examine publication bias, the study employed the trim-and-fill strategy.It was found that the pooled HRs for OS and DFS/PFS/RFS were 1.914 (95% CI: 1.689-2.168)and 2.162 (95% CI: 1.697-2.755),respectively, which demonstrated that the meta-analysis results remained robust despite the presence of publication bias.

Verification in bioinformatics databases
To further confirm our findings, we investigated if EIF5A2 could serve as a prognostic biomarker across various types of cancer.Our results demonstrated that the expression of EIF5A2 was significantly different in 27 types of cancers (p < 0.05; Figure 9) compared to healthy tissues.Additionally, univariate Cox regression analyses were conducted to evaluate the prognostic value of EIF5A2 in a wide range of   malignancies.The results showed that the overexpression of EIF5A2 was associated with poor OS in three types of cancer (p < 0.05; Figure 10a) and worse DFS and PFS in two and six cancer types (p < 0.05; Figure 10b and c).Furthermore, we used the GEPIA online tool to assess EIF5A2 expression across 31 types of cancers.The patients were divided into EIF5A2 high and low expression groups based on the median value, and the results (Figure 11) confirmed that EIF5A2 overexpression was linked to shorter OS and DFS in patients with cancer.These findings, which were    consistent with the conclusions of our meta-analysis, suggest that EIF5A2 could be a promising prognostic biomarker for various types of cancer.

Discussion
Metastasis, the most deleterious hallmark of cancer, remains responsible for a substantial proportion of cancer-related deaths [27].The interplay between autophagy and EMT, two critical processes that govern cellular behavior, has emerged as an underlying molecular mechanism driving tumorigenesis and metastasis [28].Notably, androgen receptor (AR) signaling governs the expression of EIF5A2 in androgendependent cells, promoting prostate cancer metastasis by inducing EMT and elevating EIF5A2 expression [29].Autophagy, an adaptive stress response that degrades unwanted organelles and biomolecules, contributes to the immunosuppressive environment that facilitates tumor initiation and progression [30].Drug resistance in cancer cells reduces the effectiveness of current treatments for many types of malignancy, including chemotherapy and targeted therapies [31].Many studies have studied the function of EMT in tumor drug resistance, and various EMT-mediated signaling pathways are involved in drug resistance [32].EIF5A2 has been implicated in promoting drug resistance in various malignancies.In HCC, for instance, elevated EIF5A2 levels mediate chemo-resistance by suppressing autophagy-mediated cell death [18].Hypoxia further amplifies EIF5A2 expression in NSCLC, thereby promoting cisplatin resistance via autophagy induction [33].Similarly, in breast cancer cells, overexpression of EIF5A2 correlates with lower sensitivity to doxorubicin [34].In addition, recent studies suggest that EIF5A2 might regulate cellular aging by modulating transcriptional activity, adding another layer of complexity to its diverse roles in various biological processes [35].The p-value, risk coefficient (HR), and CI of EIF5A2 in multiple tumors are analyzed by univariate cox regression.ACC: adrenocortical carcinoma; BLCA: bladder urothelial carcinoma; BRCA: breast invasive carcinoma; CESC: cervical squamous cell carcinoma and endocervical adenocarcinoma; CHOL: cholangiocarcinoma; COAD: colon adenocarcinoma; ESCA: esophageal carcinoma; GBM: glioblastoma multiforme; HNSC: head and neck squamous cell carcinoma; KICH: kidney chromophobe; KIRC: kidney renal clear cell carcinoma; KIRP: kidney renal papillary cell carcinoma; LGG: brain lower-grade glioma; LIHC: liver hepatocellular carcinoma; LUAD: lung adenocarcinoma; LUSC: lung squamous cell carcinoma; MESO: mesothelioma; OV: ovarian serous cystadenocarcinoma; PAAD: pancreatic adenocarcinoma; PCPG: pheochromocytoma and paraganglioma; PRAD: prostate adenocarcinoma; READ: rectum adenocarcinoma; SARC: sarcoma; SKCM: skin cutaneous melanoma; STAD: stomach adenocarcinoma; TGCT: testicular germ cell tumors; THCA: thyroid carcinoma; THYM: thymoma; UCEC: uterine corpus endometrial carcinoma; UCS: uterine carcinosarcoma; UVM: uveal melanoma.
Given the critical involvement of EIF5A2 in tumor-specific mechanisms such as EMT, autophagy, and drug resistance, it represents a promising target for developing novel therapeutic approaches.A meta-analysis conducted in our study corroborates the association between EIF5A2 overexpression and poor prognosis in solid tumors, underscoring the potential of EIF5A2 as a reliable and informative biomarker of malignancy outcome.
This meta-analysis is subject to several limitations.First, the sample sizes of all included studies were relatively small, and hence, the accuracy of their data may be compromised.Second, clinical characteristics of the studies were not made available.Third, there exists a notable publication bias for survival outcomes, potentially resulting from variations in research methodologies, clinical experience of authors, statistical analysis, and adjustment factors.Finally, most of the retrospective investigations were conducted in Asia, thereby limiting the generalizability of the outcomes to other regions.
As previously discussed, EIF5A2 has been implicated in tumor initiation, progression, metastasis, and chemotherapy resistance, making it a promising prognostic marker for solid malignancies.Robust prognostic markers not only enable personalized treatment for each patient by allowing for the early identification of high-and low-risk individuals, but also improve overall clinical outcomes.Despite the potential significance of EIF5A2 as a prognostic biomarker, its clinical relevance in solid tumors is still not well established.Thus, our meta-analysis aimed to comprehensively explore the potential clinical utility of EIF5A2 in solid malignancies.

Figure 2 :
Figure 2: Forest plot of the relationship between overexpression of EIF5A2 and OS.

Figure 3 :
Figure 3: Forest plot of the relationship between overexpression of EIF5A2 and DFS/PFS/RFS.

Figure 4 :
Figure 4: Forest plot of the relationship between expression of EIF5A2 and lymph node metastasis: LN, lymph node.

Table 1 :
Search strings

Table 2 :
Elements of relevant studies Study

Table 3 :
Subgroup analysis for OS HR: Hazard ratio.